Cutting hard steel members is difficult. Mild steel can be cut by saws with teeth that are harder than the mild steel member that is to be cut. When the member to be cut is as hard as or harder than saw teeth, the member cannot be cut by a saw. Harder materials for cutting are found in abrasive grinding wheels.
Grinding wheels are usually rigid and relatively thick. To sever a hard member into two pieces with a rigid grinding wheel, it is necessary to grind a section of the member the width of the grinding wheel into small particles. Such grinding procedures waste material, take time and generate heat. Heat tends to anneal the workpiece adjacent to the severed end, thereby reducing strength of the workpiece. Heat also makes it difficult to manually hold or manipulate a workpiece.
Hardened steel members can also be severed by heat with a cutting torch. Cutting torches employing oxygen and acetylene gas remove a substantial quantity of material when employed in a torch to cut through a workpiece. Some cutters employing heat, such as plasma cutters, remove a relatively small quantity of material. All of the cutting systems employing heat leave a rough surface and tend to change the hardness of material adjacent to the cut. It is generally necessary to grind the end of a member after it has been cut by heat. Grinding can remove material that has been annealed and leave an undamaged surface adjacent to the cut. The additional grinding step is time consuming and adds cost.
Flexible abrasive cutting disks have been developed in recent years. These abrasive cutting disks make relatively thin, quick cuts. They can cut material that is too hard to be cut by some other systems. Abrasive cutting disks can also cut softer material such as mild steel conveniently and in less time than some previously employed cutting systems. Due to the flexibility of the disks, they can drift axially and cut in an incorrect position. High speed abrasive disks also generate heat. The heat may cause some annealing. A workpiece is usually held in a fixed position by a clamp or other holder and the cutting disk is moved into contact with the workpiece. Clamping takes time. Other cutters employ an expensive powered carriage for either the workpiece or the cutter disk for accurate cutting. The carriages do not solve the disk flexibility problem or the clamping problem.